Many modern technologies, such as computers and smartphones, are built on the principles of Physics Topics such as quantum mechanics and information theory.
Structure and Working of Human Ear
The cars are the sense organs which help us in hearing sound. We will now describe the construction and working of a human ear. A highly simplified diagram of human ear is shown in Figure.
Construction of Human Ear
The ear consists of three compartments: outer ear, middle ear and inner ear (see Figure). The part of ear which we see outside the head is called outer car. The outer ear consists of a broad part called pinna and about 2 to 3 centimetres long passage called ear canal. At the end of ear canal is a thin, elastic and circular membrane called ear-drum (see Figure). The ear-drum is also called tympanum. The outer ear contains air.
The middle ear contains three small and delicate bones called hammer, anvil and stirrup. These ear-
bones are linked to one another. One end of the bone called hammer is touching the ear-drum and its other end is connected to the second bone called anvil (see Figure). The other end of anvil is connected to the third bone called stirrup. And the free end of stirrup is held against the membrane over the oval window of inner ear (see Figure). The middle ear also contains air. The lower part of middle ear has a narrow tube called ‘eustachian tube’ going to the throat. Eustachian tube connects the middle ear to throat and ensures that the air pressure inside the middle ear is the same as that on the outside.
The inner ear has a coiled tube called cochlea. One side of cochlea is connected to the middle ear
through the elastic membrane over the oval window. The cochlea is filled with a liquid. The liquid present in cochlea contains nerve cells which are sensitive to sound. The other side of cochlea is connected to auditory nerve which goes into the brain (see Figure). We will now describe the working of ear.
Working of Human Ear
The sound waves (coming from a sound producing body) are collected by the pinna of outer ear (see
Figure). These sound waves pass through the ear canal and fall on the ear-drum. Sound waves consist of compressions (high pressure regions) and rarefactions (low pressure regions). When the compression of sound wave strikes the ear-drum, the pressure on the outside of ear-drum increases and pushes the ear-drum inwards. And when the rarefaction of sound wave falls on the ear-drum, the pressure on the outside
of car-drum decreases and it moves outward. Thus, when the sound waves fall on the ear-drum, the ear drum starts vibrating back and forth rapidly.
The vibrating ear-drum causes a small bone hammer to vibrate. From hammer, vibrations are passed
on to the second bone anvil and finally to the third bone stirrup. The vibrating stirrup strikes on the
membrane of the oval window and passes its vibrations to the liquid in the cochlea. Due to this, the liquid in the cochlea begins to vibrate. The vibrating liquid of cochlea sets up electrical impulses in the nerve cells present in it. These electrical impulses are carried by auditory nerve to the brain. The brain interprets these electrical impulses as sound and we get the sensation of hearing.
We have just seen that a set of three tiny bones passes on sound vibrations from the ear-drum to the liquid in cochlea. Actually, the three ear-bones, hammer, anvil and stirrup, act as a system of levers and amplify (make stronger) the vibrations of ear-drum by more than 20 times. Thus, the function of three tiny bones in the middle ear is to increase the strength of vibrations coming from the ear-drum before passing them on to the inner ear. Please note that it is necessary to make the sound vibrations stronger (or amplified) because the nerve cells in cochlea respond only to strong vibrations in the liquid of cochlea.
We should not put anything (like pin, pencil or pen, etc.) inside our ears. This is because they can tear the ear-drum. The tearing of ear-drum can make a person deaf. Our ears are very delicate organs. We should take proper care of our ears and protect them from damage.